Precast garden steps

ABSTRACT

A knock-down precast stairway, preferably for installation on sloping hillsides, made up or precast tread and unique riser elements lending themselves to ridge-and-valley interrelation near the front edge, and an improved deeper set riser contributing to an overall more stabilized installation. The unique, substantially increased overall riser height is preferably approximately twice the finished riser height. It has an integrally formed tread-supporting shelf provided approximately midway the extreme top and bottom edges of each riser element so as to establish a finished step rise of approximately 7 or 8 inches which is normally comfortable. The tread-supporting shelf preferably extends across the full lateral width of the riser element. The riser portion contributing to the added overall height thereof resides in that portion which extends substantially below the tread level, and which lower extended portion is adapted to uniquely set in a preferably relatively fine crushed stone bedding or other suitable trough below the natural terrain surface. The attendant unique installation provides a normally unyielding foundation of increased stability since the bottom edges of the respective riser elements are well below the natural sloping ground surface and are essentially permanently protected from wind and rain erosion as well as most frost upheavals. Any ground engageable portion of the top and bottom treads is also set upon a bed of finely crushed stone and/or packed coarse sand to better protect it against the aforesaid elements.

Unite States tent 1 Tate 1 June 4,1974

1 1 PRECAST GARDEN STEPS [76] Inventor: John F. P. Tate, 2819 Westhampton Ave. S.W., Roanoke, Va. 24015 [22] Filed: July 26, 1973 [21] Appl. No.: 382,657

Primary Examiner-John E. Murtagh Attorney, Agent, or Firm-John E. Becker [57] ABSTRACT A knock-down precast stairway, preferably for installation on sloping hillsides, made up or precast tread and unique riser elements lending themselves to ridgeand-valley interrelation near the front edge, and an improved deeper set riser contributing to an overall more stabilized installation. The unique, substantially increased overall riser height is preferably approximately twice the finished riser height. it has an integrally formed tread-supporting shelf provided approximately midway the extreme top and bottom edges of each riser element so as to establish a finished step rise of approximately 7 or 8 inches which is normally comfortable. The tread-supporting shelf preferably extends across the full lateral width of the riser element. The riser portion contributing to the added overall height thereof resides in that portion which extends substantially below the tread level, and which lower extended portion is adapted to uniquely set in a preferably relatively fine crushed stone bedding or other suitable trough below the natural terrain surface. The attendant unique installation provides a normally unyielding foundation of increased stability since the bottom edges of the respective riser elements are well below the natural sloping ground surface and are essentially permanently protected from wind and rain erosion as well as most frost upheavals. Any ground engageable portion of the top and bottom treads is also set upon a bed of finely crushed stone and/or packed coarse sand to better protect it against the aforesaid elements.

12 Claims, 9 Drawing Figures Z 26' DRY PACKING PATENTED JUH 4 4 sum 1 8F 2 FIG.l.

PRECAST GDEN STEPS BACKGROUND OF THE INVENTION This invention relates to an improved knock-down outdoor stairway made up of a plurality of precast tread and unique riser elements, preferably for garden 'or sloping hillside use, and which lend themselves to being prefabricated in a factory, stocked in supply houses with other building material inventory and easily transportable in knockdown condition to the ultimate hillside installation site. The invention also relates to an improved method of and overall system for installing the steps.

Heretofore there have been many different types of precast or prefabricated stair units adaptable for site installation, such as those disclosed in the following prior U. S. patents. Osborn, 1,265,949; Gentile, 1,756,351; Nicols, 1,861,751; Busby, 1,964,660; Sitton, 2,939,309; and Mclntire, 3,343,316. While the steps of these foregoing patents provided a most useful service and generally satisfied the respective objectives stated therein, very few of them were readily adaptable for hillside use where the riser and elements are settable essentially directly in or upon the natural terrain surface, and without use of supporting stringers.

Heretofore, it has been the conventional practice in constructing stepways or stairways for ascending or descending sloping terrain to excavate for and build forms for the pouring of concrete to form the stepway; also, it has been customary practice to form stepways from bricks or stones, all of which involve substantial costs of materials and labor such as for bricklayers, stone masons, or other workmen. Such stairs are normally of a permanent installation and formal appearance and seldom blend with the surrounding landscape. When conventional, flat individual steps are laid on the sloped terrain, they normally tend to settle or slip, and after use become uneven and hazardous to the user, as well as unsightly in appearance.

SUMMARY OF THE INVENTION In place of the previous known precast and/or con ventional more permanent stepways, my invention provides for making precast, preferably reenforced tread and riserelements from a cementious masonry or synthetic resinous material, with improved riser elements of extra overall height, and being of a knockdown character.

The unique substantially increased overall riser height is preferably approximately twice the finished riser height. It has an integrally formed treadsupporting shelf provided approximately midway the extreme top and bottom edges of each riser element so as to establish a finished step rise of approximately 7 inches. or 8 inches which is normally comfortable. The tread-supporting shelf, preferably extends across the full lateral width of the riser element. The riser portion contributing to the added overall height thereof resides in that portion which extends substantially below the tread level, and which lower extended portion is adapted to uniquely set in a preferably relatively fine crushed stone or other suitable material in a trough below the natural terrain surface. Thus, the unique installation provides a normally unyielding foundation of increased stability since the bottom edges of the respective riser elements are well below the natural sloping ground surface and are essentially permanently protected from wind and rain erosion as well as most frost upheavals. Any ground engageable portion of the top and bottom treads is also set upon a bed of finely crushed stone and/or packed coarse sand to better protect it against the aforesaid elements.

While the riser element, with its preformed intermediate shelf to support the back edge of a tread element, is usually made in a fairly uniform height dimension, the tread elements are made in a variety of front-torear sizes, or with custom ordered dimensional variations of both riser and tread elements to better adapt to sloping terrain having a wide range of differing degrees of inclination, such as set forth in a chart hereinafter.

My improved stepway also lends itself not only to improved and more stable installation and assembly, but also can be readily disassembled for removal and/or relocation to another location or more preferred site if so desired.

Therefore, it is a principal object of this invention to provide an improved method of and step component apparatus for installing knockdown, precast stepways particularly upon terrain of varying slope and usually between upper and lower relating level areas.

Another primary object is to provide an improved prefabricated step unit of the foregoing character which may be readily assembled and disassembled.

Still another object is to provide simple and economically feasible stepway or stairway components by which the risers and treads can be made in separate simplified molds or forms which are conducive to provide more accessible tamping and smoothing of the fresh mixed cementious or plastic material.

The foregoing and other objects and advantages will become more evident from the following more detailed description taken in conjunction with the following illustrative drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. I is a side elevational view of an exemplary set of steps depicting a typical installation for a ground slope of approximately 45, or I to 1 ratio, with the ter rain shown in cross-section;

FIG. 2 is a view like FIG. 1 but depicting a typical in-- stallation in which the slope of the terrain is approximately 34, or representative of a 1%. to 1 ratio, and showing a modified form tread to riser interconnection;

FIG. 3 is a front elevational view of the assembled steps of FIGS. 1 and 2;

FIG. 4 is a side view showing my alignment and positioning system for properly installing the precast unique riser elements;

FIG. 5 is a front elevation of the system components depicted in FIG. 4;

FIG. 6 is a diagrammatic figure of a typical hand rail preferred for use with the steps;

FIG. 7 is a perspective view of my novel precast riser element;

FIG. 8 is an enlarged fragmentary detail view showing one form of a ridge and valley type of complemental mating of the forward portion of the tread and riser elements; and

FIG. 9 is a chart illustrative of the required relative sizes of the riser and tread elements for different sloping terrain expressed in ratio form.

DESCRIPTION OF A PREFERRED EMBODIMENT Like reference characters will denote like parts in the several drawings. Referring in more detail to the drawings, particularly FIGS. I-3, the assembled steps as a whole are generally designated 10, and comprise a plurality of precast, generally planar, tread elements 12 and riser elements 14. As is relatively customary, suitable complemental ridge and valley means designated 16 in FIG. 1 are provided to interconnect the forward edge portion of the tread 12 with the upper edge of the riser 14. In FIG. 2, a different dowel pin and recess hole means 1%, such as an embedded pin and tube arrangement, is illustrated.

The riser element I4 is deemed to be unique in the combination of a tread-supporting shelf 20, disposed to support the tread 112 at a comfortable step height from the next succeeding tread, and a lower projecting extension portion 22. Portion 22 is of substantial extent to contribute to a riser having a substantially increased overall height than the riser elements of other precast or prefabricated step elements among prior art of which I am aware. While these riser elements are susceptable to custom fabrication in varying dimensions of width and height, the general proportion of these unique riser elements is such that the overall height thereof is approximately twice the dimension of the exposed finished step rise. While these relative dimensions may vary, the riser element will have a lower body portion extending below the tread-supporting means a distance preferably at least approximately one half of the distance between tread surfaces of successive installed tread elements. Inasmuch as customary rise heights are between 7 inches and 8 inches in most installations, then deducting for the thickness of the tread element supported on the top edge of the riser, reduces the exposed riser height accordingly. In a preferred form the tread thickness of a precast concrete step may be as much as 2 inches whereas for one fabricated of a synthetic resinous or other suitable material, including rot-resistant chemically treated wood, the thickness may be approximately 1 inch. Regardless of the tread thickness, the extra depth of the riser should be sufficient to extend well below the natural surface of the terrain, with or without the use of a crushed stone foundation, so that for most geographical areas it will not be notably affected by frost upheavals, or normal surface erosion.

As illustrated, the risers M are installed so that the lower extension is seated within a suitable depth trough-like excavation 24. In most all preferred installations, the excavation is filled partially with relatively small crushed stone 26 which when packed will not shift after the front and rear sides of the riser are further packed with more crushed stone. The use of the crushed stone or similar dry aggregate provides not only a stable and readily adjustable (during installation) base and packing, but also a drainage field to help dissippate any surface water which may tend to collect thereat.

Due to both the sloping terrain and pervious nature of the embedment and packing for the riser elements, very little water, if any at all, will collect around the riser base. There maybe some terrain which is naturally sandy or inherently more suitable to self-draining and in which the installation may be effected without the use of crushed stone.

In the FIG. I 45 slope installation, the intermediate tread elements will necessarily have a lesser tread dimension from front to back than for the more gentle slope depicted in FIG. 2. In the former, the finished tread dimension may approximate 8 inches-l0 inches whereas is FIG. 2 it may approximate 12 inches-l4 inches, depending upon the taper or style of the nosing edge. The top tread in each of FIGS. l and 2 are provided with a greater front-to-back dimension than those of the intermediate treads, so as to bridge onto stable terrain which is also preferably provided with a crushed stone bedding either with or without a moditied riser cut off at tread level.

The tread and riser elements are preferably made with suitable strength-reenforcing wires or mesh (not shown), particularly including portions extending into the area of the shelf 20. The edges of the precast members are preferably oppositely beveled to make them more easily removed from the mold. Although there is shown a gap at the rearward edge adjacent the riser, due to said bevel, it may be left open, or arbitrarily filled with a cement or caulking composition (not shown) as desired. Even if water should collect and freeze in the bevel area, it will not do any damage, since it would merely cam upwardly therefrom.

Because in the forms of FIGS. I and 2 the components remain essentially the same, and the basic difference resides in degree of slope, the same but primed reference numerals have been used therein.

Referring to the ridge and valley (or tongue and groove) arrangement, shown in more detail in FIG. 8, the depth of the valley 15a is preferably slightly greater than the height of the ridge 15b so as to assure stable load bearing of the front of the tread along the top edge of the riser element 14.

PREFERRED METHOD OF INSTALLATION Installation begins with the site selection, and establishing the location of a pair of upper horizontal working points WP, shown in FIGS. 4 and 5. These working points will be then marked by a straight piece of approximately 1 inch X 4 inches lumber 28 spanning the proposed step width, and then nailed to suitable stakes 30, driven into the ground, or otherwise suitably anchored and/or clamped into position at laterally opposite sides of the chosen site. Similar working points WP are established at the bottom of the slope where the lower step will terminate, and in alignment with the working points at the top of the slope. Reference characters WP, 28 and 30' designate these corresponding elements and measuring layout. Intermediate the upper stakes 30, there is preferably a tread-establishing L- shaped jig member 31 suitably connected to the spanning member 28. The foot of the L, designated 32, corresponds to shelf 20 and is preferably used to better 10- cate the top tread, and from which to project to locate the top edge of the riser member 14.

The difference between the top and bottom elevation is then carefully measured by use of a straight datum board 33 (FIG. 4), level and rule or tape measure. The total rise between the bottom and top sets of working points is determined and, if necessary, slightly adjusted to accomodate division into multiples of approximately 7 inches to 8 inches, or to whatever the ultimately desired riser height might be. Next, the total horizontal run is measured and divided by the number of risers, previously determined, to obtain the approximate front-to-back width of each tread. Reference to the chart exemplified in FIG. 9, will enable a selection from the several potentially available precast treads. Using such a selected tread width, this figure is multiplied by the number of risers to give a final dimension for the total horizontal run. The working points then may be adjusted as necessary, and finally located with the aid of the necessary tools such as plumb bob, spirit level and datum plank.

The terrain in between the top and bottom working points is then smoothed along the incline in conformance with the guide strings stretched therebetween. Then by use of a relatively narrow spade, preferably about 6 inches wide, the excavations 24 are dug in the appropriately spaced areas, and to the predetermined depth to allow approximately a 2 inch thick footing of crushed stone or like material beneath the bottommost edge of the riser. 1 preferably use a unique and novel riser-positioning jig designated generally at 34 in H65. 4 and 5. FlG. 34 comprises a wide flat board, such as a piece of plywood 36, which exceeds the front-to-back width of the desired tread. Attached beneath the board are two pair of angle members 38, spaced toward opposite sides of the steps. Each pair of members has the angle straps thereof spaced apart to provide a slip-fit over the riser element. The members 38 are spaced at the desired requisite dimension from the datum edge 40, which edge initially is placed on the shelf 32 in alignment with the top working points WP.

Installation preferably commences with the top riser gauging off of the shelf 32 connected to the staked board 28. Its accurate elevation, and square alignment with the parallel guide strings, is as important as the accurate positioning of all the other steps in the flight, since it will determine the elevation and alignment of the next lower riser. The setting of all the risers will proceed from top to bottom, each succeeding riser depending for its accurate positioning, on the accuracy of the preceding riser, using the positioning jig and spirit level, rubber tapping mallet, and other aids and tools as preferred. Placing of the tread slabs may be best deferred until all the riser slabs are installed and packed firmly and unyieldingly in place with the crushed stone. After the risers are firmly installed in accordance with the foregoing preferred method, the tread slabs or elements are placed to bridge between two successive risers. The rear edge of the tread slab l2 rests upon the shelf 20 and the triangular ridge b on the underside of the front portion complementally seats in the valley 15a recessed into the top edge of the riser slab. Alternately, as per H6. 2, the interconnection may be made by the dowel pin and recessed tube arrangement.

The foregoing unique and novel construction and manner of interlocking provides a very stable and rigid step assembly. It is not preferred to cement the tread and risers together at either the front or rear seating.

While it is believed that the two forms for slopes shown in FIGS. 1 and 2 will fit many of the slopes encountered in actual practice, a table has been evolved, as per FIG. 9, for which precast elements are to be produced to have in stock and available to cover nine different tread widths. These are intended for use with risers having a finished riser or step height of 8 inches, and to accomodate slopes of varying inclinations or ratios between 1:1 and 3:1 in progressive uniform intervals. Experience has shown that most selected sites can be graded in a 3 to 4 foot wide strip to conform to any of the chart-listed slopes and related tread and riser data.

My improved precast stairs as described herein are equally well suited for use in established residential areas, new housing developments, public parks, grounds of public and commercial buildings and many other potential locations. Installation of the precast relatively lightweight components is achievable by one or two man crews without the need for time-consuming costly forms, the latter of which are often poorly erected. This avoids the messy and arduous process of pouring and finishing concrete, or the like, at the sites, which are often inaccessible to large heavy concrete trucks.

By use of my improved step elements and method and system of installing, architecturally aesthetic superiority is gained over on site pouring of concrete, thereby assuring smooth and uniform factory finish, color and material and workman quality. Additionally, these precast steps are aesthetically enhanced by the nosing projection of the treads, which feature is nearly invariably omitted in poured concrete steps due to the difficulty in forming appropriate forms etc.

Accordingly, it is apparent that a novelly improved method, apparatus and system of installing my improved precast steps, which is rapid accurate and neat, has been evolved which satisfies all of the basic objectives and advantages set forth in the preamble and throughout this application. Contemplated modifications include providing the bottom edge of the riser with an optional widened foot area; the riser and tread elements may have reduced thickness medial areas to reduce weight; and the shelf 20 may be non-continuous in longitudinal length, such as a series of spaced lug or bracket members, not shown.

While specific exemplary embodiments have been described and illustrated in some detail, still other variations and modifications may be made by those skilled in the art without departing from the preceding inventive spirit and concepts, and reference should be made to the appended claims for the scope of the invention as defined therein.

1 claim:

1. A stair for installation on inclined terrain including a combination of a plurality of precast separate tread and riser elements interrelated with one another and said terrain, said tread elements each having a forward and rearward portion; said riser elements each includmg a. a generally elongated rectangular body with a top edge for cooperatively supporting the forward portion of said tread element,

b. an oppositely disposed bottom edge;

c. tread-supporting means formed with and transversely projecting from said body so as to support said rearward portion of said tread element at predetermined, easily traversible step height between successive tread elements; and

d. said riser body having an overall height between said top and bottom edges substantially in excess of said predetermined distance between said top edge and said tread-supporting means so as to provide a substantial lower riser body portion extending below said tread-supporting means a distance at least approximately one half of the distance between tread surfaces of successive installed tread elements, whereby e. said lower body portion of said riser element is adapted to have a substantial portion thereof compactly embedded in an excavation in the sloping terrain.

2. A stair as defined in claim 1, wherein said treadsupporting means on said riser element includes an integrally formed projecting shelf of sufficient longitudinal length to stably support said tread element at opposite end and intermediate portions thereof.

3. A stair as defined in claim 1, wherein said top edge of said riser element and said forward portion of said tread element have complemental mating means for stably but releaseably properly aligning and interlocking said tread and riser elements when in proper assembly as a stair.

4. A stair as defined in claim 11, wherein said riser and tread elements are precast of a settable concreteforming material including reenforcing means.

5. A stair as defined in claim il, wherein said riser and tread elements are precast of synthetic resinous materials including strength-reenforcing means.

6. A stairway as defined in claim ll, wherein said lower body portion of said riser element has a downwardly projecting height below the tread-supporting means equal to at least approximately that of the exposed rise between successive treads.

7. In a knockdown stairway for installation on inclined terrain and composed of a plurality of precast separate tread and riser elements consecutively interrelated with one another, said tread elements having forward and rearward portions and edges, the improvement of a novel riser element having a generally elongated rectangular planar body with a top edge for supporting the forward portion of said tread element, an oppositely disposed bottom edge, tread-supporting means integrally formed with and transversely projecting from said planar body so as to support said rearward portions of said tread element at a predetermined level to provide a comfortable and easily traversible step rise between successive tread elements; and said riser body having an overall height between said top and bottom edges substantially in excess of said predetermined distance between said top edge and said tread-supporting means so as to provide a substantial lower riser body portion extending well below said tread-supporting means a distance at least approximately one half of the distance between tread surfaces of successive installed tread elements, whereby said lower body portion of said riser element adapted to have a major portion thereof compactly embedded in an excavation in the sloping terrain.

8. A stairway as defined in claim '7, wherein said tread-supporting means on said riser element includes an integrally formed projecting shelf of suificient longitudinal length to stably support said tread element at opposite end and intermediate portions thereof.

9. A stairway as defined in claim 7, wherein said top edge of said riser element and said forward portion of said tread element have complemental mating means for stably but releaseably properly aligning and interlocking said tread and riser elements when in proper assembly as a stair.

it). A stairway as defined in claim '7, wherein said tread and riser elements are relatively proportioned and disposed so that said tread elements have a nosing edge which projects forwardly of said riser element.

11. A stair for installation on inclined terrain including a combination of a plurality of precast separate tread and riser elements interrelated with one another and said terrain, said tread elements each having a forward and rearward portion; said riser elements each including a. a generally elongated rectangular body with a top edge for cooperatively supporting the forward portion of said tread element,

b. an oppositely disposed bottom edge;

c. tread-supporting means formed with and transversely projecting from said body so as to support said rearward portion of said tread element at predetermined, easily traversible step height between successive tread elements; and

d. said riser body having an overall height between said top and bottom edges substantially in excess of said predetermined distance between said top edge and said tread-supporting means so as to provide a substantial lower riser body portion extending below said tread-supporting means a distance at least sufficient to permit a substantial ground penetration thereby, whereby c. said lower body portion of said riser element is adapted to have at least a substantiai portion thereof compactly penetrated into a complementary formed depression or excavation in the terrain.

creased stabilization in said excavation. 

1. A stair for installation on inclined terrain including a combination of a plurality of precast separate tread and riser elements interrelated with one another and said terrain, said tread elements each having a forward and rearward portion; said riser elements each including a. a generally elongated rectangular body with a top edge for cooperatively supporting the forward portion of said tread element, b. an oppositely disposed bottom edge; c. tread-supporting means formed with and transversely projecting from said body so as to support said rearward portion of said tread element at predetermined, easily traversible step height between successive tread elements; and d. said riser body having an overall height between said top and bottom edges substantially in excess of said predetermined distance between said top edge and said tread-supporting means so as to provide a substantial lower riser body portion extending below said tread-supporting means a distance at least approximately one half of the distance between tread surfaces of successive installed tread elements, whereby e. said lower body portion of said riser element is adapted to have a substantial portion thereof compactly embedded in an excavation in the sloping terrain.
 2. A stair as defined in claim 1, wherein said tread-supporting means on said riser element includes an integrally formed projecting shelf of sufficient longitudinal length to stably support said tread element at opposite end and intermediate portions thereof.
 3. A stair as defined in claim 1, wherein said top edge of said riser element and said forward portion of said tread element have complemental mating means for stably but releaseably properly aligning and interlocking said tread and riser elements when in proper assembly as a stair.
 4. A stair as defined in claim 1, wherein said riser and tread elements are precast of a settable concrete-forming material including reenforcing means.
 5. A stair as defined in claim 1, wherein said riser and tread elements are precast of synthetic resinous materials including strength-reenforcing means.
 6. A stairway as defined in claim 1, wherein said lower body portion of said riser element has a downwardly projecting height below the tread-supporting means equal to at least approximately that of the exposed rise between successive treads.
 7. In a knockdown stairway for installation on inclined terrain and composed of a plurality of precast separate tread and riser elements consecutively interrelated with one another, said tread elements having forward and rearward portions and edges, the improvement of a novel riser element having a generally elongated rectangular planar body with a top edge for supporting the forward portion Of said tread element, an oppositely disposed bottom edge, tread-supporting means integrally formed with and transversely projecting from said planar body so as to support said rearward portions of said tread element at a predetermined level to provide a comfortable and easily traversible step rise between successive tread elements; and said riser body having an overall height between said top and bottom edges substantially in excess of said predetermined distance between said top edge and said tread-supporting means so as to provide a substantial lower riser body portion extending well below said tread-supporting means a distance at least approximately one half of the distance between tread surfaces of successive installed tread elements, whereby said lower body portion of said riser element adapted to have a major portion thereof compactly embedded in an excavation in the sloping terrain.
 8. A stairway as defined in claim 7, wherein said tread-supporting means on said riser element includes an integrally formed projecting shelf of sufficient longitudinal length to stably support said tread element at opposite end and intermediate portions thereof.
 9. A stairway as defined in claim 7, wherein said top edge of said riser element and said forward portion of said tread element have complemental mating means for stably but releaseably properly aligning and interlocking said tread and riser elements when in proper assembly as a stair.
 10. A stairway as defined in claim 7, wherein said tread and riser elements are relatively proportioned and disposed so that said tread elements have a nosing edge which projects forwardly of said riser element.
 11. A stair for installation on inclined terrain including a combination of a plurality of precast separate tread and riser elements interrelated with one another and said terrain, said tread elements each having a forward and rearward portion; said riser elements each including a. a generally elongated rectangular body with a top edge for cooperatively supporting the forward portion of said tread element, b. an oppositely disposed bottom edge; c. tread-supporting means formed with and transversely projecting from said body so as to support said rearward portion of said tread element at predetermined, easily traversible step height between successive tread elements; and d. said riser body having an overall height between said top and bottom edges substantially in excess of said predetermined distance between said top edge and said tread-supporting means so as to provide a substantial lower riser body portion extending below said tread-supporting means a distance at least sufficient to permit a substantial ground penetration thereby, whereby e. said lower body portion of said riser element is adapted to have at least a substantial portion thereof compactly penetrated into a complementary formed depression or excavation in the terrain.
 12. Stair apparatus as defined in claim 11, wherein said riser bottom edge of paragraph (b) is provided with an enlarged foot area to thereby contribute to increased stabilization in said excavation. 